Pump for use in hydraulic transmission of power



March 27, 1945. w R GROVES 2,372,375

PUMP FOR USE IN HYDRAULIC TRANSMISSION OF POWER Filed May 25, 1943II/jII/ll/ 'between' them, and the two" Patented Mar. 27, 1945 I PUMPFOR USE IN HYDRAULIC TRANSMISSION OF POWER.

Walter Robert Groves, Wolverhampton, England, assignor to TurnerManufacturing Company,

Limited, Wolverhampton, England Application May 25,1948, Serial No.488,433

In Great April 25, 1942 10 Claims. (Cl. 103-37) The invention relates tohydraulic pumps used in connection with hydraulic power transmission;

and, while it is more immediately concerned with hand operated pumps forhydraulic power systerns on aircraft, it is also applicable to otherhydraulic power transmission systems, and also to power operated pumpsfor such purpose.

It has become usual to operate certain parts of aircraft, for instancethe undercarrlages and bomb doors, by hydraulic means-operated, in somecases, by power from the engines when such are running, but operated, atother times, by hand. The method is to pump liquid into an operatingcylinder in which is a movable piston. operable under liquid pressure ineither direction. For most of the travel of the piston of said cylinderthe pressure required to move it is relatively small; but, at some pointof the stroke,

the pressurerequired is relatively great. Hence for hand operation thepump plunger has had to be of relatively small diameter with the resultthat only a relatively small quantity of liquid is pumped into theoperating cylinder at each stroke of the pump, so that a relativelylarge amount of time is taken in importing the full movement to theoperating piston.

According to this invention there are provided, in respect of thehydraulic system, two pumps, one of which has preferably a largercapacity than the other, both pumps being operated from the same sourceof power during the main part of the transmission of power, the one pumpbeing cut out or short-circuited automatically when the pressure in thehydraulic system reaches .a predetermined value.

The cutting out or short-circulting of the one pump may be efie'cted bya spring-pressed plunger carrying a valve or being adapted to engagewith a valve, in either case to Open a passage leading from the.delivery to the suction side of the one pump, such lunger being exposedto pressure from the delivery side of the other pump (which is not cutout) and also to the general hydraulic system, a non-return valve beingprovided to prevent flow of liquid from the said system back into theshort-circuited pump.

The two pumps may be arranged side-by-side with the spring-pressedplunger and its chamber p pistons may connect to the two ends of a votedlever fitted with a handle by which it may be rocked by hand. Y

The pumps may be of the single acting or double acting or differentialThe spring-pressedplunger above referred to may slide within a chamberexposed at the top manner already well known; and each piston rod to thedelivery pressure and open at the bottom to the suctionpassage, and suchchamber may cut across a passage joining the delivery sides of the twopumps this passage being widened at such place to form an annularchamber. Thespring-pressed plunger has a transverse port or annulargroove communicating with an axial passage in the plunger which servesto keep the transverse port in communication with the suction passage.Hence, when theplunger has,been moved a given distance by deliverypressure, the said port enters the annular chamber, and so openscommunication between the suction an delivery sides of the one pump;

One important application of the invention is t presses for mouldingplastics, and other hydraulic presses, where the primary and largerportion of the stroke of the ram oflers little resistance and cantherefore be operated quickly with advantage; whereas a high pressure isessential at the last part of the stroke.

A convenient embodiment of the invention is described with reference tothe accompanying drawing which is a vertical section with some of thearts shown in elevation.

In this drawing, A is the pump shell comprising two pump cylinders B, C,of the same diameter and in which work two pistons 13, E, of the samediameter, but the stroke of the piston E is longer than that of thepiston D. Otherwise the two pistons are identical.

For reciprocating the pistons there is provided a three-armed lever Fpivoted at F and having one arm f forming a handle, a short arm fconnected to the piston D by a connecting rod d, and a longer arm fconnected to the piston E by a connecting rod e.

Each of the pistons has a hollow piston rod e'- having an externalcross-sectional area which is one half the cross-sectional area of thepiston, so as to render the pump double-acting in a passes at its upperend through a packing ring c and guide ring'c' pressed down by' a ring'c screwed into the top of the cyllnden. Both con-- necting rods connectwith their respective piston rods at points well down in relationthereto and by bail joints e. They connectat their upper ends to thelever F by pivot joints e G is an inlet passage leading to the undersides of the two cylinders Band C at the bottom of each of which is avalve H pressed by a coil spring 71. on' to a rubber seating h. As eachpiston goes up it can therefore draw oil into the respective cylinder,but such oil cannot return;

' power, and means by jwhich the one pump is lower than the groove sothat when the piston is moving down the ring lies against the upper wallof the groove e leaving a space below it 6 whereas, when the pistonmoves up, the space occurs above the ring. In its lowermost position thering covers ports e leading to the space in the cylinder above the valveH. Ports e lead from the groove e to the space in the cylinder above thepiston.

J is an oil delivery passage connecting directly to the 'upper end ofthe cylinder B but only indirectly with the cylinder C by way of thecylinder B and a passage K in which is placed a springpressed non-returnball valve is.

M is a plunger adapted by slide in a sleeve m set in the pump shell, theplunger being constantly pressed in an upward direction by a coil springm. The plunger M has a head m at its upper end of somewhat increaseddiameter such head Ming adapted to seat down on the top of the sleeve mwhen the plunger is fully down.

The sleeve mhas an internal annular passage m communicating with thepassage K so that oil can pass from the cylinder C along such passageand around the plunger M. In the latter is an annular groove m whichcommunicates by a central passage m with a space m which is incommunication with the inlet passage G. N is a passage leading to aspace n above the sleeve mfrom the passage K between the cylinder B andthe non-retum valve k.

When oil is required to be delivered at a relatively high rate, and at arelatively low pressure, the plunger M is kept up by its spring. Bothpump pistons are then pumping oil, the piston D, directly to thedelivery J, and the piston E to the delivery J by way of the passage K,valve is and upper part of the cylinder B. The major A!) part of the oilis pumped by the piston E because or its "longer stroke.

\ the oil. is no longer able to viiow at a high :rate it experiences asudden rise of pressure which is communicated to the top of the plungerM by way of the top of the cylinder B and passages-K and N but it is, ofcourse, not transmitted past the ball valve k. The pressure sotransmitted forces down the plunger M until '0 the head m seats on thetop of the sleeve m. As the diameter oi the headm' is greater than thatof the interior of the sleeveit tends to assist in holding the plungerdown. In this lowermost pos tion or the plunger M the groove 1",

' coincides with the annular recess m thus putting the portion of thepassage K which is to the right of the non-return valve k, incommunication wit the inlet passage .6. The piston E then simply pumpsoil back to the, inlet passageand offers little resistance to movement.The oil is now. pum ed wholly by the piston D which has by far theshorter stroke so that's. much increased pressure at a slower te canbemaintained.

,Having. fully .d' bed my inventi n what I claim and desire to secure byLetters Patent is: r I claim: I c 1. A pump unit for hydraulic powertransmis, on com risingtwo separate pum s arranged side by side. aleverlinking the pistons to ether. a. pivot mounting offset from the centerof said lever whereby one piston has-o. longer stroke than the other. asource of power from'which both said umps are driven ,both pumps beingoperative during the main port-of the transmission or automaticallyrendered inoperative when the pressure in the hydraulic system reaches apredetermined value. I

2. A pump unit for hydraulic power transmission comprising two separatepumps oi diflerent capacity, a pivoted lever connecting the pistons, anoffset pivot mounting for said lever, the pistons having diilerentlengths of stroke, an arm on said lever forming a handle, a source ofpower from which both pumps are driven, both pumps being operativeduring the main part of the transmission of power, and means by whichthe pump of larger capacity is automatically rendered inoperative whenthe pressure in the hydraulic system reaches a predetermined value.

3. A pump unit for hydraulic power transmission comprising two separatepumps the pistons of which are of the same diameter but of which onepiston has a longer stroke than the other, a lever connecting saidpistons, an offset mounting for said lever, and an arm on the leverfunctioning as a handle, the pistons being arranged side by side inspaced relatioma source of power from which both pistons are driven,both pistons being operative during the main part 0! the transmission ofpower, and means by which the pump having the piston of longer stroke isautomatically rendered inoperative when the pres-' surein the hydraulicsystem reaches a predetermined value.

4. A pump unit for hydraulic power transmission comprising two separatepumps, a'threearmed lever from which the pistons of both the pumps aredriven by connecting rods which connect the respective pistons with twoof the arms of said three-armed lever, the said lever having an oii'setmounting whereby the pistons will have different lengths of stroke, bothpumps being operative during the main part of the transmission of powerand means by which the one pump is automatically rendered inoperativewhen the pressure in the hydraulic system reaches a predetermined value.

5. A pump unit for hydraulic power transmission comprising two separatepumps, a hollow piston rod of each said piston, a three-armed lever, anoffset mounting on which said lever is pivoted, two connecting rodspivotally connected to two arms of sa d three-armed lever and connectedto points well down within said hollow piston rods near to therespective pistons, both pistons being operative during the main parttive when the pressure in the hydraulc system reaches apredeterminedvalue, the pistons having strokes oi different lengths.

6. A pump unit for hydraulic power transmission comprising two separatepum s spaced laterally from each other and being of different lengths,athree-armed lever, a shorter and a longer arm of said three-armed lever,pistons or said pumps, connect'ng rods by which the one i piston havinga shorter stroke is driven from the said shorter arm, and the otherpiston having a ion erstroke is driven tromthe said longer arm, bo pumpsbeing operative during the main part of thetransmission or power andmeans by which the pump having the piston or longer 0 stroke;automatically rendered inoperative when the pressure in the hydraulicsystem reaches a predetermined value.

7. A pump unit for hydraulic power transmission comprising two pumps, asource of power from which both said pumps are driven,-both pumps beingoperative during the main part oi the transmission of power but the onepump being automatically rendere inoperative when the pressure in thehydraulic system reaches a given value, a spring-pressed plunger, achamber within which said plunger works, a valve in said plunger, apassage leading from the delivery to the suction side of said pump, thesuction side being rendered inoperative. said plunger being exposed topressure from the delivery side of the pump (the delivery side of thepump not being rendered inoperative) and to the general hydraulicsystem, a passage connecting the delivery sides of the two pumps, anon-return valve in said passage, and said valve of said plungernormally closing the said passage connecting together the suction'anddelivery sides of the pump which is rendered inoperative, but operatingto open such passage by the action of said plunger when the pressure inthe hydraulic ystem reaches a predetermined value.

8. A pump unit for hydraulic power transmission comprising two pumps, asource 01' power from which both said pump are driven, both pumps beingoperative during the main part of the transmission of power but the onepump being automatically rendered inoperative when the pressure in thehydraulic system reaches a given value, a spring-pressed plunger, achamber within which said plunger works, a valve of said plunger, apassage leading from the delivery to the suction side or said pump whichis rendered inoperative, said plunger exposed to pressure from thedelivery side of the pump which is not rendered inoperative and to thegeneral hydraulic system, a passage connecting the delivery sides of thetwo pumps, a non-return valve in said passage, and said valve oi saidplunger normally closing the said passage connecting together thesuction and delivery sides of the pump which is rendered inoperative,but operating to open such passage by the action of said plunger whenthe pressure in the hydraulic system reaches a predetermined value, achamber within which said plunger is adapted to slide, said chamberbeing exposed at one end to the pressure in the system, said chambercutting across the said passage connecting the delivery sides of the twopumps and being widened out where it crosses said passage, a peripheralrecess of said plunger, an axial passage of said plunger communicatingwith said peripheral recess, said recess ooinciding with saidwidened-out portion when said plunger is pressed against the force orits spring by increase of pressure in the system.

9. A pump unit for hydraulic power transmission comprising two pumps, asource of power from which both said pumps are driven, both pumps beingoperative during the main part of the transmission of power, but the onepump being automatically rendered inoperative when the pressure in thehydraulic system reache a given value, a spring-pressed plunger, achamber within which said plunger works, a valve of said plunger, apassage leading from the delivery to the suction side oi. said pumpwhich is rendered inoperative, said plunger being exposed to pressurefrom the delivery side of the pump which is not rendered inoperative andto the general hydraulicsystem, a passage connecting the delivery sidesof the two pumps, a non-return valve in said passage, and said valve ofsaid plunger normally closing the said passage connecting together thesuction and delivery sides of the pump which is rendered inoperative,but operating to open such passage by the action ofsaid plunger when thepressure in the hydraulic system reaches a predetermined value, and ahead of increased diameter which closes down on the end or said chamberwhen the plunger has moved to its fullest extent under the increasedpressure 0! oil in the system.

10. A pump unit for hydraulic power transmission comprising two pumps, apiston of each pump, a deep peripheral annular groove in one or eachpiston. a packing ring in such groove, said packing ring being shallowernarrower than the groove, ports connecting said groove with the space onthe delivery side of the piston, ports connecting the groove with thesuction side of the pistonand said packing ring adapted to close suchsecond mentioned ports during the movement oi the piston away from thesuction end of the respective pump, a source or power from which bothsaid pumps are driven, both pumpsbeing operative during the main part ofthe transmission oi power and means by which the one pump isautomatically rendered inoperative when the pressure in the hydraulicsystem reache predetermined value. I

WALTER. ROBERT GROVES.

